How to use NGrams in Lucene?

Hello everyone,

I've been assigned to the task of implementing an NGrams-Based index and search in Lucene. Now, from what I've seen in the API, there are NGramsTokenizers and other related classes, but how do I *use* them? Moreover, the term "n-gram" is used in multiple ways in Lucene: it refers to token-based n-grams as well as character-based n-grams. I would need to make use of letter-based n-grams.

Any clues on how to do this? I'm sitting here for hours now, and Google is not very helpful in this case...